If sin(x)= 1/3 and sec(y)= 5/4 where x any lie between 0 and pi/2, evaluate cos(x+y)
Answer:
First sin(x)=1/3, and it’s in the first quadrant , i.e. 0<x<pi/2, then x =arcsin(1/3)=19.47 degrees. Same way sec(y)=5/4, then cos(y)=4/5, y =arccos(4/5)=36.86989 degrees ,
cos(x+y)=cos(19.47+36.86989)=0.55426
